Biology subjects

Ramming, A.

Publications and source records attributed to Ramming, A..

4 recordsLinked to original sources

bioRxiv2025

Disease-specific fibroblast-myeloid interactions in rheumatoid arthritis synovium

Rheumatoid arthritis (RA) is characterized by profound remodeling of the synovial microenvironment. Here we show that enhanced fibroblast-macrophage cross-talk distinguishes RA from psoriatic arthritis (PsA). MerTK-SPP1 macrophages represent the dominant inflammatory myeloid population in RA, interacting with expanded fibroblast subsets through SPP1-mediated signaling. Lining fibroblasts display induction of antigen-presentation and IL-6/JAK-STAT pathways, while a CHI3L1-producing fibroblast population arises specifically in RA and may act as a source of autoantigens. These stromal populations interact closely with FABP5 iDC3 cells and T cells within a disrupted synovial lining, creating a niche driving adaptive immune activation. In contrast, PsA exhibits increased fibroblast- endothelial interactions without major endothelial transcriptional changes. Our data identify SPP1 signaling and fibroblast-myeloid-dendritic interactions as core drivers of RA synovial inflammation that links innate immune activation to the initiation of autoimmunity. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=78 SRC="FIGDIR/small/688477v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@c76e39org.highwire.dtl.DTLVardef@11563a9org.highwire.dtl.DTLVardef@141f3fborg.highwire.dtl.DTLVardef@f90742_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

Distinct myeloid precursors and their interaction with mesenchymal cells orchestrate the spreading of psoriatic disease from the skin to the joints

Psoriatic disease initially affects the skin, but later extends to the joints. Herein, we describe a two-step process that orchestrates spreading of inflammation from the skin to the joints. Induction of psoriatic skin disease in photoconvertible mice, followed by sequencing and computational characterization of skin-derived cells in the joints, identified a unique population of CD2+ MHC-II+ CCR2+ myeloid precursors that built up a skin-derived myeloid cell compartment in the joints. Single-cell cross-species reference mapping and mitochondrial variant tracing showed an orthologue human cell population. Interactome analyses in the joints showed that in a second step, resident regulatory CD200+ fibroblasts critically regulate the priming of the CD2+ MHC-II+ CCR2+ myeloid precursors, which subsequently regulate the IL-17 expression in T cells. Hence, spreading of inflammation requires a distinct migratory myeloid precursor population and a permissive local tissue environment, similar to tumour metastasis. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/665302v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@38c440org.highwire.dtl.DTLVardef@dc574dorg.highwire.dtl.DTLVardef@1e79f72org.highwire.dtl.DTLVardef@19508cf_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2023

GDF15 mediates inflammation-associated bone loss through a brain-bone axis

Metabolic mediators play an important role in regulating chronic inflammation in the body. Here we report an unexpected role for GDF15 (Growth Differentiation Factor 15), a central mediator of food intake, in inflammation-associated bone loss. GDF15 serum levels were found to be elevated in arthritis patients and inversely correlated with bone density. Despite being associated with inflammation, we found that GDF15 itself does not cause, nor contribute to, clinical or histopathological arthritis. Rather, under inflammatory conditions, GDF15 mediates trabecular bone loss through its receptor GFRAL, which is exclusively expressed in the hindbrain. GDF15-GFRAL binding results in {beta}-adrenergic activation of MALPs (Marrow Adipocytic Lineage Precursors) in the bone marrow, which stimulate osteoclasts and trigger bone loss. These data suggest a metabolic mediator-controlled brain-bone axis in inflammation, through which bone loss is induced in a contextual rather than general manner. These findings may lead to more specific therapeutic interventions to protect bone.

immunology↗

bioRxiv2023

Molecular Imaging with Fibroblast Activation Protein Tracers depicts Inflammatory Joint Damage and its Transition to Resolution of Inflammation

Joint fibroblasts play an important role in the transition from joint inflammation to irreversible joint damage. There is no established clinical method to measure fibroblast activation during inflammation and their phenotypic dynamics upon therapy to date. Here we show that upon treatment with IL-17A/TNF-blocking antibodies fibroblasts change their phenotype from a destructive IL-6+/MMP3+THY1+ to a CD200+DKK3+ subtype, actively inducing resolution of inflammation. This phenotypic switch can be visualized due to so far unexplored different capacities of fibroblast subtypes with regard to receptor internalization of small molecular tracers with high affinity to FAP. Although FAP expression levels are comparable between fibroblast subtypes in the joint, FAP internalisation rate correlates with the destructive potential of fibroblasts and resolving fibroblasts have a lower FAP internalisation rate, providing a valuable imaging tool to visualize the transition from joint damage to resolution of inflammation.

immunology↗